1. Field of the Invention
This invention relates to hydrocarbon production and reservoir water disposal.
2. Description of the Prior Art
Various methods have been used or proposed for the production of hydrocarbons. The most common method of oil removal involves the use of pumps in which mechanical equipment is placed in the well. Other approaches which have limited application involve gas lift or gas displacement techniques. However, gas displacement techniques are suitable only for shallow wells.
Many oil wells, particularly in the latter stages of the producing life of a well, produce large quantities of salt water. Handling this water represents significant expense in withdrawal, separation and disposal. Various methods have been employed for extracting the oil from the unwanted water. In most cases the total yield is pumped to the surface of the well and various methods used for separating the oil from the water. The unwanted water is pumped downwardly again into a disposal stratum through a disposal well.
A common problem associated with the presence of water is water coning caused by pressure gradients associated with the flow of reservoir fluids, particularly at high production rates. This can lead to premature abandonment of the well.
Some prior proposals have approached the problem of water coning by pumping water back into the formation. One example of such proposals is described in U.S. Pat. No. 4,241,787 E. H. Price. The system described utilized conventional downhole pumps and separator for oil production and water disposal.
More recently a "Downhole Water Loop--A New Completion Method to Minimize Oil Well Production Watercut in Bottom-water-drive Reservoirs" was proposed by A. K. Wojtanowicz and published by The Journal of Canadian Petroleum Technology. The water loop method contemplates a second set of perforations below the original oil water interfaces. Production of water from the lower perforations would reduce or eliminate water coning.
Another example is U.S. Pat. No. 5,296,153 to B. R. Peachey in which is proposed a "Method and Apparatus for Reducing the Amount of Formation Water in Oil Recovered from an Oil Well". This patent proposes using a hydrocyclone separator which separates water and oil in the wellbore. The fluids are pumped using downhole electric motor and pumps. Water is disposed of into a lower formation with oil and some water produced to the surface. This method of dealing with higher water production has limited application due to high costs inherent in the design and method of operation.
A similar approach is proposed in U.S. Pat. No. 4,805,697 to C. Fouillout, "Method of Pumping Hydrocarbons with an Aqueous Phase and Installation for the Carrying out of the Method" in which a static separator is used which works on a similar principle as the hydrocyclone separator. Again implementation and operation of this method appear costly with limited application.